Hi I would look at fixing a bit of your stocking first - how big is the tank like in length and width? How big are the Clown Loaches. When you say Grammies do you mean Gouramis? If so what kind of Gourami, what do they look like? And what kind is the Knife Fish, what does it look like?
How many Red Tailed sharks do you have? You only really want one per tank as other wise you get a dominant and a submissive one and the submissive one will constantly be harassed and attacked until it is dead basically...
And the Bala Shark would be better off rehomed to be honest as your tank is not large enough to handle a school of them and thats what they need.
As for bottom dwellers - you already have some in the Clown Loaches which to be fair you could do with getting more of, at least in the short term as they will eventually outgrow your tank. But if the tank is a nicely sized four foot or better yet a five foot they will be okay for a few years.
In this kind of tank shrimp will possibly get eaten by the other fish you have. I was going to suggest if you like Snails a couple of suitable species but there is a good chance your Clown Loaches would eat them so thats a no go. Also never put Crabs in a community tank as the odds are at some point they will catch and eat one of the fish or at best catch and injure the fish.
For me the important thing is to get your tank into great shape with your stocking, getting the fish that will outgrow the tank or live in misery or under threat from others out and getting in others that suit your taste and thrive in this tank. Ultimately it just leads to a stressful situation for you and the fish.
Based on what you have at the moment you have a pretty easy route into a well balanced tank IMO This is the stocking I would suggest
6 Red Line Torpedo Barbs - to replace your Bala Shark, similar appearance (if not better)
6 Gourami - best to find out what species you have fist but cant see a problem over all
1 African Brown Knife Fish - again see which you have first but if its a Black Ghost, Glass or Clown Knife it will outgrow the tank
1 Red Tailed Shark
6 Yoyo Loaches - or any of the medium sized loaches like polka dot, histronica, zebra all will do well - this is to replace your Clown Loaches.
If you want to add more, which would be fine you have room
Perhaps some kind of Synodontis Catfish would do well.
Hope its helped, its meant to. Sorry if its harsh but its often best to get straight to the point.
Wills
